Patent GB-637791-A (GB)
Title: Improvements in or relating to antenna systems and radio and like coupling arrangements
IPC: H01Q5/00
Filed: 1946-08-01
Abstract: 637,791. Aerials ; aerial coupling devices MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 1, 1946, No. 22984. Convention date, May 30, 1942. [Classes 40 (v) and 40 (vii)] An aerial system comprises a closed loop transmission line to different points on which is connected a plurality of aerial elements and feeder lines, the points being so positioned that the difference in the two paths through the transmission line between the connecting points of any two aerials and between the connecting points of any two feeder lines is an odd integral number of half-wavelengths and the difference in the two paths between the connecting point of each feeder line and the connecting point of each aerial element is an integral number of wavelengths. The application of the invention to an overlapping-beam system is shown in Figs. 2, 5 and 6, and comprises two groups of antennµ consisting of centre antennµ 1 and 3 and associated side antennae 5, 7 and 9, 11 respectively, the corresponding antennµ of each group being energized in phase quadrature with respect to each other, the centre antennae constantly, while the polarities of the side antennae are alternately reversed to produce a resultant field which is deflected from side to side with respect to a centre reference line. To produce the required difference in direction of the two lobes each centre antenna is made of four quarter-wave sections, Figs. 4 and 5, and the component dipoles 31, 33 and 35, 37 energized in phase as two half-wave antennae by means of the arrange - ment shown in Fig. 5 in which, because of the connection of the dipoles in reverse polarity, the dipoles 33 and 37 are fed through a transmission line 41 which is A/2 greater, with respect to points 45 and 47, than that feeding the dipoles 31 and 35. Consequently any difference in the currents of the component dipoles of each centre antenna (e.g. due to coupling with the side antennae) is prevented. In accordance with the invention the junction points 45 and 47 and consequently the antennae 1 and 3 are energized in phase quadrature by connecting points 45 and 47 to a closed transmission line loop 41 on which supply points 49 and 51, connected together through two paths different in length by #/2, are supplied with energy in quadrature phase by means of the transmission line 61 and flaring stubs 55 and 57. Fig. 6 shows the arrangement of the side antennae which are connected to the junction points 45 and 47 of a closed transmission line loop, similar to that employed with the arrangement of Fig. 5, through a transmission line 44. The dipoles of each antenna are connected in opposite polarities to the line so that they radiate 180 degrees out of phase. To provide periodic reversal of the polarities of the side antennµ the feed line 63 is connected to a supply line 71 alternately through two paths differing in length by #/2 by means of a closed transmission line loop 67, 69 the points 75 and 77 of which are arranged to be alternately short circuited by means indicated at 79. To effect the necessary power division between the centre antennae and the side antennµ an arrangement comprising two parallel #/4 transmission line sections 81, 83 and a #/4 section 85, acting as an impedance inverter, is connected between the side antenna array feed line 71 and the main feed line 93 so that the impedance presented at the junction 91 by the side antennae is four times that presented by the centre antenna feed line 61.